A filled aquarium is far heavier than most people expect. A quick rule of thumb: a full freshwater tank weighs about 10 lb per gallon once you count the glass, water and gravel. Rock and decor push it higher.
Where the weight comes from
- Water: about 8.34 lb per US gallon (1 kg per litre). This is most of the total.
- Glass: from about 7 lb for a 5 gallon tank to over 200 lb for a 125 gallon.
- Substrate: a 2 inch gravel bed weighs roughly 100 lb per cubic foot. Use the substrate calculator for your tank.
- Rock and decor: live rock or large stones can add 1 lb per gallon or more.
Fish tank weight by size
Figures below assume a standard glass tank, fresh water and a 2 inch gravel bed. Select a tank for its full dimensions.
| Tank | Empty glass | Water | 2 in gravel | Total, filled |
|---|---|---|---|---|
| 5 gallon | 7 lb | 42 lb | 15 lb | 64 lb |
| 10 gallon | 11 lb | 83 lb | 23 lb | 118 lb |
| 20 gallon | 25 lb | 167 lb | 33 lb | 225 lb |
| 20 gallon long | 25 lb | 167 lb | 42 lb | 233 lb |
| 29 gallon | 40 lb | 242 lb | 42 lb | 324 lb |
| 30 gallon | 43 lb | 250 lb | 50 lb | 343 lb |
| 40 gallon breeder | 58 lb | 334 lb | 75 lb | 467 lb |
| 50 gallon | varies | 417 lb | 75 lb | varies by brand |
| 55 gallon | 78 lb | 459 lb | 72 lb | 609 lb |
| 60 gallon | varies | 500 lb | 72 lb | varies by brand |
| 75 gallon | 140 lb | 626 lb | 100 lb | 866 lb |
| 90 gallon | 160 lb | 751 lb | 100 lb | 1,011 lb |
| 100 gallon | varies | 834 lb | 150 lb | varies by brand |
| 125 gallon | 206 lb | 1,042 lb | 150 lb | 1,398 lb |
Choosing a stand
Use a stand made for aquariums and rated for at least the full weight in the table. Furniture such as dressers and bookcases isn't designed for a constant, concentrated load and can sag or fail. The stand should be level, and the tank should sit flat on its frame or a leveling mat, depending on the manufacturer's instructions.
Floor load for big tanks
A 75 gallon tank puts about 865 lb on a footprint of about 6 square feet. Most modern floors handle that when the stand runs across the joists and sits near a load-bearing wall. Above about 100 gallons, or in older buildings and upper floors, it's worth asking a builder or structural engineer.
Saltwater tanks weigh more
Saltwater is about 3% heavier than fresh water, and reef tanks often carry live rock and a sump below the stand. Add those to the figures above when planning a marine tank.
Frequently asked questions
How much does a 55 gallon fish tank weigh full?
About 600 lb once set up: roughly 78 lb of glass, 459 lb of water and around 70 lb of gravel. Rock and decor add more.
How much does a gallon of aquarium water weigh?
Fresh water weighs about 8.34 lb per US gallon. Saltwater is roughly 3% heavier, around 8.6 lb per gallon.
Can my floor hold a fish tank?
Small and mid-size tanks on a proper stand are fine on most floors. For large tanks, place the stand across the floor joists and near a load-bearing wall, and ask a builder if you are unsure.